1. Technical Field
The present invention relates to a releasing device, a fixing device and an image forming apparatus.
2. Related Art
An image forming apparatus wherein paper onto which a toner image is transferred is thermally compressed by a fixing device so that the toner image is fixed on the paper is provided with a releasing device to quickly release the paper after the fixing process from the heating roll of the fixing device and to prevent the paper from winding around the heating roll.
The releasing device is provided with a releasing guide (an example of a releasing unit) that is installed so that a very small gap (for example, approximately 0.5 mm) is maintained between the tip of the releasing guide and the heating roll. The releasing device releases the paper having passed through a fixing portion formed between the heating roll and a pressure roll by scooping up the tip of the paper.
It is considered appropriate that the releasing guide, disposed close to the heating roll that is heated to a high temperature, should be made of metal having a small thermal deformation amount so that the above-mentioned gap is stably maintained. However, since the releasing guide is disposed at a position that is located near a paper discharge port and might be touched by the user's hand when a paper jam is cleared, it is unfavorable that the releasing guide is made of metal and heated to a high temperature.
For these reasons, it is desirable that the releasing guide is made of resin instead of metal. However, in the case that the releasing guide is made of resin, the releasing guide is deformed locally and eventually makes contact with the heating roll, whereby image quality degradation occurs.
It is also considered that the releasing guide is made of resin and backed with sheet metal to suppress thermal deformation. However, in this case, a mechanism for maintaining the potential of the sheet metal at ground potential is required to prevent charging.